I can't answer for BudP, the designer, but I can tell you that you can easily tell by simply trying it! And the simplest way to test it is what was suggested earlier: a 6" loop of ordinary zip cord (18 AWG). Put them anywhere you want to test the effect. It's a crude approximation, but it does work and will tell you the tale within minutes (though full break in takes much longer). The real thing is more refined and revealing, of course.

I found that just on my speaker side was enough to convince me this had real merit. Immediate results; immediate grins. Added them to my amp side negs of the speaker outputs; again, immediate grins. Added them then to the sub with uncertain results, but no downside. Replaced all the quick and dirty zip loops with a carefully constructed set made of Litz wire and all sounded much better. Then did the RCA versions to my receiver (common ground, I assume), my DAC and my CDP. Again, all these added something delightful.

Only the sub versions are not clearly beneficial that I can detect, but that does not mean they aren't contributing, just that it would be hard to detect there in the LF output. Part of the reason for that, to my thinking, is because one of the more obvious and profound benefits of the speaker and amp versions is the immediate articulation of the LF anyway. So what a sub version adds is not as audible, as the basic speaker set is quite startlingly revealing in LF.

It was so good that I simply refuse to take them out to test what does what where!

bcharlow, thanks for your input.
The two sets of spade GC's arrived yesterday.
Initially I put one pair on the speakers, then quickly added the other set to the amp -ve terminals.
Bass is definitely better defined and has more impact, but more importantly it sounds like a layer of colouration has been removed from the speakers - allowing more realism, space/air, image separation and vocal intelligibility.

I have some experimentation to do, but I will listen for a while with the links in their current location.

BTW, upon consideration locating a GC on the ground post of my preamp may not be appropriate.
My current Plinius electronics use ground lift switches on all components to connect/disconnect signal ground from chassis ground. Currently I have all ground switches 'lifted' - ie not connected to chassis ground.
Since the preamp ground post is connected to the chassis (see photo below), a GC loop here wouldn't provide much benefit to the signal board (I would think).
Curiously, lifting the ground switches on the Plinius amps provided a similar sort of effect - though not as pronounced - as use of the GC loops.

Speedskater, like I said above, this preamp is designed to allow 'lifting' of the chassis ground from the signal ground.
All signal grounds connect to the PCB ground.
The switch in the top right hand corner connects signal ground to the chassis (or not).
I've never used the XLR connectors, maybe there is something technically wrong with this arrangement (?) - but Plinius seem to know what they're doing:

Here's something weird.
I connected one of the spade GC's to the the ground post of the preamp (directly connected to the chassis, top right of pic above, just under the switch).
With the switch in the ground 'lift' position I expected the GC to have no effect - but I appear to get a further subtle improvement along the same lines as the amp/speaker connected GC. Closing the switch (signal ground to chassis) seems to introduce some smearing, a slight loss of clarity/presence.

I do beleive the XLR ground should go to the chassis instead of signal ground. For RCA connection, it's a bit different if you have ground lift. I think there is a nice tutorial on the AES site on grounding. Just using a switch to connect to chassis ground may be misleading because location of ground connection matters.

I do beleive the XLR ground should go to the chassis instead of signal ground. For RCA connection, it's a bit different if you have ground lift. I think there is a nice tutorial on the AES site on grounding. Just using a switch to connect to chassis ground may be misleading because location of ground connection matters.

While this is getting OT, looking at my pic above it's hard to tell where exactly the XLR ground shield is connected. It doesn't appear to be connected to the same thick ground track as the RCA grounds.
Quite possible they are connected to a 'chassis' ground located on the PCB - 'chassis' ground on the pcb would be kept separate to signal ground (connected with the switch).

Here is another pic taken near the XLR/RCA outputs.
Note the ground screw middle left - the location of this ground screw is close to the incoming safety ground - see above pic for perspective.

This is damn near impossible to make. I wrapped 30 gauge 100 times and now I have 200 ends of magnet wire to strip and try and solder together.

Acid flux did not help to remove the varnish.

Anyone have a chemical that will strip the wire for soldering? I have a real rats nest if I try and rake sandpaper over the ends.

Best bet would be to pick up a solder pot; MCM has a nice little one for c. $30, and once you have it you'd be surprised at how often you'll find yourself using it for all sorts of projects. Once you've twisted wires together (and perhaps lightly coated the ends with a bit of flux), simply dipping the ends of the wire into the molten solder in the pot for a few seconds will both strip the insulation and leave the ends neatly soldered together in one step.

Are you dipping both ends or just the far end and then connecting the pigtail to the two ends at the top?

Sorry -- my 3:00AM brain thought it was writing more clearly, but my daylight brain sees the ambiguities! I have been dipping each end of the wire separately, giving me a length that has both ends stripped of insulation and tinned with solder. Then, after removing any residual dross, I've been soldering each prepared end to the spade or RCA. Maybe others will respond with their own techniques; I'm curious if anyone's had success intertwining the ends before tinning, creating the loop at the same time.